Cationically curable silicone compositions based on colloidal silica and anti-mist/anti-fouling hard coatings formed therefrom

ABSTRACT

Silicone compositions that are cationically crosslinkable into hard, anti-mist/anti-fouling coatings, e.g., onto thermoplastic substrates, contain colloidal particles of non-functionalized silica and also: at least one crosslinkable and/or polymerizable silicone monomer, oligomer and/or polymer comprising: at least one structural unit of formula (I): 
 
Z 1 (R 0 ) a SiO (3−a)/2   (I) 
in which: a=0, 1 or 2;  
     the radicals R 0 , which may be identical or different when a &gt;1, are each an alkyl, cycloalkyl, aryl, vinyl, or alkoxy radical, or a hydrogen atom;  
     the radicals Z 1 , which may be identical or different when the number of units of formula (I) is greater than 1, are each an organic substituent comprising at least one epoxy and/or alkenyl ether and/or oxetane and/or dioxolane and/or carbonate reactive functional group; and a total number of silicon atoms per molecule at least equal to 2; and an effective amount of at least one cationic initiator; and optionally, at least one organic solvent.

CROSS-REFERENCE TO PRIORITY/PCT APPLICATIONS

This application claims priority under 35 U.S.C. § 119 of FR 02/15946,filed Dec. 16, 2002, and is a continuation of PCT/FR 2003/003614, filedDec. 8, 2003 and designating the United States (published in the Frenchlanguage on Jul. 29, 2004 as WO 2004/063300 A1; the title and abstractwere also published in English), each hereby expressly incorporated byreference and each assigned to the assignee hereof.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to compositions which can be crosslinkedby the cationic route to provide hard scratch-resistant coatings.

More preferably, the present invention relates to compositions which canbe crosslinked by the cationic route to provide hard coatingsfurthermore exhibiting anti-fouling and/or anti-mist properties.

2. Description of Background and/or Related and/or Prior Art

Thermoplastics, such as polycarbonate, have acquired a predominant rolein numerous applications as substituents for glass. This is the case,for example, in the automobile field, where they are used for themanufacture of lenses for the headlamp units and tail lights ofvehicles. This is also the case in the field of the spectacle trade,where they are used for the manufacture of spectacle glasses. The mainadvantage of these thermoplastics is that they are lighter and lessbrittle than glass.

However, these materials also exhibit a major disadvantage, namely,their low hardness in comparison with that of glass. Consequently, thesematerials are more easily subject to scratching and to detrimentalchanges, even in the context of normal use.

Need thus continues to exist for solutions to limit these problems ofscratching and of detrimental change.

One of the solutions employed consists in producing a hard coating atthe surface of the thermoplastic, in the form of a transparent laminateintended to improve the performance of the thermoplastic. Numerousdocuments of the state of the art disclose compositions intended to formthis type of coating.

Compositions based on epoxyalkoxysilanes which can be crosslinked by thethermal route are described in U.S. Pat. No. 4,211,823. Thesecompositions make it possible to obtain hard polysiloxane coatings.

A significant disadvantage of these compositions is the time necessaryfor the crosslinking.

WO-A-94/10230 provides an improvement for avoiding excessively longcrosslinking times. This improvement consists in using ultravioletradiation as means for activating the crosslinking. However, adisadvantage of these compositions is that of having a poorer resistanceto abrasion than that of the coatings crosslinked by the thermal route.

In order to overcome this disadvantage, WO-A-02/00561 claims a processfor the manufacture of a coating obtained by crosslinking, by thecationic route, an epoxy monomer essentially based on glycidyl, first byphotopolymerization and then by thermal post-crosslinking in thepresence of a thermal crosslinking catalyst.

U.S. Pat. No. 6,210,790 claims a colloidal silica modified by epoxy orpropenyl ether groups and introduced into compositions which can becrosslinked by the cationic route to give a hard coating. The colloidalsilica is grafted with the alkoxysilane in water. In addition to thesilica functionalized by the alkoxysilane, the composition comprisesmultifunctional monomers and in particular siloxane monomers with epoxyunits and a cationic initiator of onium salt type.

One disadvantage of the technique described in this patent is, first,that it involves the preliminary functionalization of the colloidalsilica by an alkoxysilane and, secondly, that it is necessary to removethe solvent for functionalization of the silica before carrying out thecrosslinking.

Furthermore, the industries in the technical fields under considerationremain vigilant for hard coatings also having anti-mist and/oranti-fouling properties.

Some prior documents disclose means which make it possible to obtainanti-mist or anti-fouling properties have already been described.

This is the case in particular with WO-A-02/12404, which describes ahard coating based on colloidal silicas which are functionalized byacrylates for optical devices exhibiting anti-fouling properties via alayer of perfluoropolyether deposited on the hard coating.

FR-A-2,749,587 describes a composition which can be crosslinked byradiation to give a hard coating exhibiting anti-mist properties. Thiscomposition comprises a colloidal silica, an olefin comprising at leasttwo sites of unsaturation and at least one divalent oxyalkylene radical,and a trialkoxysilane comprising an olefinic functional group.

The anti-mist coating obtained from the composition described inFR-A-2,749,587 has the principal disadvantage of being sensitive toinhibition by atmospheric oxygen.

However, no composition of the prior art is capable of providing a hardcoating jointly exhibiting anti-mist and anti-fouling properties. Thisis because the mechanisms of the anti-mist and anti-fouling propertiesare generally incompatible.

SUMMARY OF THE INVENTION

Novel compositions which can be cured by the cationic route to providehard coatings have now been discovered.

Briefly, the present invention features compositions capable of forminghard coatings exhibiting anti-mist and/or anti-fouling properties.

The present invention also features compositions capable of formingcoatings possessing permanent anti-mist and/or anti-fouling properties.

Thus, the present invention features compositions which can becrosslinked by the cationic route to provide hard coating, comprisingcolloidal particles of non-functionalized silica, and additionally whichcomprise:

-   -   at least one crosslinkable and/or polymerizable silicone        monomer, oligomer and/or polymer comprising:    -   at least one structural unit of formula (I):        Z¹(R⁰)_(a)SiO_((3−a)/2)  (I)        in which:

a=0, 1 or 2;

the radicals R⁰, which may be identical or different when a≧1, are eachan alkyl, cycloalkyl, aryl, vinyl, or alkoxy radical, or a hydrogenatom, preferably a lower C₁-C₆ alkyl radical;

the radicals Z¹, which may be identical or different when the number ofunits of formula (I) is greater than 1, are each an organic substituentcomprising at least one epoxy and/or alkenyl ether and/or oxetane and/ordioxolane and/or carbonate reactive functional group, Z¹ preferablybeing an organic substituent comprising at least one epoxy and/ordioxolane reactive functional group;

-   -   and a total number of silicon atoms per molecule at least equal        to 2, and    -   an effective amount of at least one cationic initiator, and    -   optionally, at least one organic solvent.

DETAILED DESCRIPTION OF BEST MODE AND SPECIFIC/PREFERRED EMBODIMENTS OFTHE INVENTION

The term “hard coating” means a coating having a pencil hardness atleast equal to H.

Advantageously, the subject compositions additionally comprise, asanti-mist compound, at least one crosslinkable and/or polymerizablesilicone monomer, oligomer and/or polymer comprising at least onestructural unit of formula (II):Z²(R⁰)_(a)SiO_((3−a)/2)  (II)in which:

a=0, 1 or 2;

R⁰ is as defined above;

the radicals Z², which may be identical or different when the number ofunits of formula (II) is greater than 1, are each an organic substituentcomprising at least one oxyalkyl or polyoxyalkyl functional group((CH₂)_(m)O)_(x) or (CH₂—CH(CH₃)—O)_(y) or copolymers, said monomer,oligomer and/or polymer exhibiting a viscosity of less than 500 mPa·sand preferably less than 300 mPa·s.

An effective compound can be, by way of example, a mixture of asilicone-polyether block copolymer and of free polyether sold under thereference Rhodorsil® Oil 10646.

An effective organic compound can also be a vinyl ether sold under thereference Rapicure® DPE2 (CAS No. 765-12-8), DVE3 (CAS No. 114188-95-3)or DPE3 (114266-85-2).

This is because it participates in the cationic polymerization and isincorporated in the network, rendering the treatment very effective.

Other anti-mist compounds can, for example, be sodium sulfosuccinate.

The anti-mist compound can also be any surfactant comprising hydrophilicgroups, such as polyoxyethylene, polyoxypropylene, alkali metal sulfate,sulfonate or carboxylate, polyols, amine salts or quaternary amines.

More advantageously still, the compositions according to the inventioncomprise, as anti-fouling compound, at least one crosslinkable and/orpolymerizable silicone monomer, oligomer and/or polymer comprising atleast one structural unit of formula (III):Z³(R⁰)_(a)SiO_((3−a)/2)  (III)in which:

a=0, 1 or 2,

the radicals R⁰, which may be identical or different, are each an alkyl,cycloalkyl, aryl, vinyl, or alkoxy radical, or a hydrogen atom,preferably a lower C₁-C₆ alkyl radical;

the radicals Z³, which may be identical or different when the number ofunits of formula (III) is greater than 1, are each an organicsubstituent comprising at least one (C_(n)F_(2n+1))—(R⁰)_(a) group withn<20; and/or one perfluoropolyether compound of formula (IV):Y—(C_(a)F_(2a)O)_(b)—C_(a)F_(2a)—Y  (IV)in which:

Y is a polymerizable group or a fluorine or hydrogen atom;

a ranges from 1 to 7;

b ranges from 1 to 300, such that said perfluoropolyether compound hasan average molecular mass of from 500 to 20,000.

The most effective organic compounds are:

-   -   perfluorinated compounds including an epoxide or vinyl ether        functional group, such as glycidyl octafluoropentyl ether,        glycidyl *tetrafluoroethyl ether, glycidyl tetrafluoropropyl        ether, glycidyl hexadecafluorononyl ether, glycidyl        dodecafluoroheptyl ether, heptadecafluorononyloxirane,        heptafluorobutyloxirane, hexadecafluorononyl ether,        hexadecafluoro-8-(trifluoromethyl)nonyloxirane,        dodecafluoro-6-(trifluoromethyl)heptyloxirane,        octafluoropentanol, heptadecafluorononanol,        heptadecafluorodecanol, and the like,    -   Asahi Glass products, such as the C₈F₁₇ oxirane.

Thus, the perfluoropolyether compound can be selected from the groupconsisting of:

-   (C₂H₅O)₂CH₃SiC₃H₆NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₃SiCH₃(OC₂H₅)₂,-   (C₂H₅O)₃SiC₃H₆NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₃H₆Si(OC₂H₅)₃,-   F(CF(CF₃)CF₂O)₂₅CF₂CF₃, C₄H₉NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₄H₉,-   CH₂═CHOOC₂H₄NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₂H₄OOCCH═CH₂,-   CH₂═CHCOOCH₂(CF₂O)₁₅(C₂F₄O)₁₃CF₂CH₂OOCCH═CH₂,-   (HOCH₂)₂CH₂NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHCH₂(CH₂OH)₂,-   (C₂H₅O)₃Si(CH₂)₃NHCO(CF₂CF₂O)₈CF₂CONH(CH₂)₃Si(OC₂H₅)₃,-   (C₂H₅O)₂CH₃Si(CH₂)₃NHCO(CF₂CF₂O)₈CF₂CONH(CH₂)₃SiCH₃(OC₂H₅)₂,-   (C₂H₅O)₂CH₃Si(CH₂)₃NHCO(CF₂CF₂O)₁₄CF₂CONH(CH₂)₃SiCH₃(OC₂H₅)₂,-   (C₂H₅O)₃Si(CH₂)₃NHCO (CF₂C(CF₃)FO)₁₂CF₂CONH(CH₂)₃Si(OC₂H₅)₃,-   (C₂H₅O)₂CH₃Si(CH₂)₃NHCO(CF₂C(CF₃)FO)₁₂CF₂CONH(CH₂)₃SiCH₃(OC₂H₅)₂ or-   OOCCH═CH₂OOCCH═CH₂-   H₂C═HCCOO—CH₂CHCH₂NHCO(CF₂O)₁₅(CF₂CF₂O)₁₃CF₂CONHCH₂CHCH₂—OOCCH═CH₂

According to a first embodiment, the cationic initiator can be selectedfrom among those having a cationic moiety selected from onium ions offormula (V):[(R¹)_(n)-A-(R²)_(m)]⁺  (V)in which:

-   -   A represents an element from Groups 15 to 17 of the Periodic        Table, such as, for example: I, S, Se, P or N,    -   R¹ represents a C₆-C₂₀ carbocyclic or heterocyclic aryl radical,        it being possible for said heterocyclic radical to comprise        nitrogen or sulfur as heteroelements,    -   R² represents R¹ or a linear or branched C₁-C₃₀ alkyl or alkenyl        radical, said R¹ and R² radicals optionally being substituted by        a C₁-C₂₅ alkoxy, C₁-C₂₅ alkyl, nitro, chloro, bromo, cyano,        carboxyl, ester or mercapto group,    -   n is an integer ranging from 1 to v+1, v being the valency of        the element A,    -   m is an integer ranging from 0 to v−1, with n+m=v+1.

Preferably, the anionic moiety of the initiator is a borate of formula(VI):[BX_(a)R_(b)]⁻  (VI)in which:

-   -   a and b are integers ranging, for a, from 0 to 3 and, for b,        from 1 to 4, with a+b=4,        -   the X symbols represent:        -   a halogen atom (chlorine, fluorine) with a=0 to 3,        -   an OH functional group with a=0 to 2,        -   the R symbols are identical or different and represent:            -   a phenyl radical substituted by at least one                electron-withdrawing group, such as, for example, OCF₃,                CF₃, NO₂ or CN, and/or by at least 2 halogen atoms (very                particularly fluorine), this being the case when the                cationic entity is an onium of an element from Groups 15                to 17,            -   a phenyl radical substituted by at least one                electron-withdrawing element or group, in particular a                halogen atom (very particularly fluorine), CF₃, OCF₃,                NO₂ or CN, this being the case when the cationic entity                is an organometallic complex of an element from Groups 4                to 10,            -   an aryl radical comprising at least two aromatic rings,                such as, for example, biphenyl or naphthyl, optionally                substituted by at least one electron-withdrawing element                or group, in particular a halogen atom, including in                particular fluorine, OCF₃, CF₃, NO₂ or CN, whatever the                cationic entity.

The initiator can advantageously be selected from the group consistingof:

-   [(C₈H₁₇)—O-Φ-I-Φ]⁺ [B(C₆F₅)₄]⁻, [(CH₃(₂—CH-Φ-I-Φ-CH₃]⁺ [B(C₆F₅)₄]⁻-   [C₁₂H₂₅-Φ-I-Φ]⁺ [B(C₆F₅)₄]⁻, [(C₈H₁₇—O-Φ)₂I]⁺[B(C₆F₅)₄]⁻-   [(C₈H₁₇)—O-Φ-I-Φ]⁺ [B(C₆F₅)₄]⁻, [(Φ)₃S]⁺ [B(C₆F₅)₄]⁻-   [(Φ)₂S-Φ-O—C₈H₁₇]⁺ [B(C₆H₄CF₃)₄]⁻, [(C₁₂H₂₅-Φ)₂I]⁺ [B(C₆F₅)₄]⁻-   [(CH₃)₂—CH-Φ-I-Φ-CH₃]⁺ [B(C₆H₃(CF₃)₂)₄]⁻-   (η⁵-cyclopentadienyl)(η⁶-toluene)Fe⁺ [B(C₆F₅)₄]⁻-   (η⁵-cyclopentadienyl)(η⁶-1-methylnaphthalene)Fe⁺ [B(C₆F₅)₄]⁻-   (η⁵-cyclopentadienyl)(η⁶-Cumene)Fe⁺ [B(C₆F₅)₄]⁻

According to an alternative embodiment of the invention, the initiatorcan also be a nontoxic onium salt having a cationic structure of formula(VII):[(CH(CH₃)₂-Φ-)-I—(—R¹)]⁺  (VII)in which the symbol R¹ represents the -Φ-R² radical, R² being a linearor branched alkyl radical comprising from 1 to 20 carbon atoms,preferably 1 to 15 carbon atoms.

The anionic structure of the onium salt is selected from the groupconsisting of: Cl⁻, Br⁻, BF₄ ⁻, PF₆ ⁻, CF₃SO₃ ⁻, N(SO₂CF₃)₂ ⁻,CH(SO₂CF₃)₂ ⁻, B(C₆F₅)₄ ⁻, B(PhOCF₃)₄ ⁻, SbF₆ ⁻ and/or AsF₆ ⁻. However,the following initiators have proved to be particularly advantageous:

-   [(CH(CH₃)₂-Φ-)-I-Φ-CH₃]⁺ Cl⁻[(CH(CH₃)₂-Φ-)-I-Φ-CH₃]⁺ B(C₆F₅)₄ ⁻-   [(CH(CH₃)₂-Φ-)-I-Φ-CH₃ ⁺ PF₆ ⁻[(CH(CH₃)₂-Φ-)-I-Φ-CH₃]⁺ B(PhOCF₃)₄ ⁻-   [(CH₃)₂—CH-Φ-I-Φ-CH₃]⁺ [B(C₆H₃(CF₃)₂)_(4]]) ⁻

Such initiators are describe in the document FR-A-2 762 001.

The silicone oligomer is represented by the following formula (VIII):Z⁴Si(R⁰)_(a)O_((3−a)/2)in which:

-   -   a=0, 1 or 2,    -   the radicals R⁰, which may be identical or different, are each        an alkyl, cycloalkyl, aryl, vinyl, or alkoxy radical, or a        hydrogen atom, preferably a lower C₁-C₆ alkyl radical,    -   Z⁴ is selected in particular from among the following radicals:

The silica used can be of various origins: precipitated silica, fumedsilica, silica aerogels, silica sol and/or natural silica.

According to a preferred embodiment of the invention, the amorphoussilica present predominantly or entirely in the silicone phase resultsfrom silica sol and more particularly from silica organosols; a generaldescription of silica sols is given in U.S. Pat. No. 2,801,185 and in“The Colloid Chemistry of Silica and Silicates” (Ralph K. IIer, CornellUniversity Press, 1955; see in particular pages 120-121).

Mention may be made, as examples of commercial silica organosols, ofthose from Clariant, Fuso Chemicals, Nalco, Degussa-Huls and DuPontChemicals.

Mention will be made, for Clariant, of the following products: Highlink®OG1-32, Highlink® OG8-32, Highlink® OG401-31, Highlink® OG502-30,Highlink® OG502-31 and Highlink® OG600-51.

The silica particles exhibit a mean diameter of less than 1 μm and morepreferably of from 50 to 500 nm.

It should be noted that the colloidal or fumed silica used to reinforcethe coating is conveyed in an organic solvent and in particular analcoholic solvent, such as primary, secondary or tertiary alcohols.Isopropanol or diacetone alcohol are solvents of choice.

Use may also be made of ketones, tetrahydrofuran, hydrocarbon fractionsor fluorinated solvents.

Preferably, the proportion of organic solvent in the compositionsaccording to the invention is at least equal to 10 parts by weight.

This invention also features a process for preparing a composition whichcan be crosslinked by the cationic route to provide a hard coating asdescribed above, which essentially comprises the stage entailing mixingparticles of non-functionalized colloidal silica with:

-   -   at least one crosslinkable and/or polymerizable silicone        monomer, oligomer and/or polymer comprising at least one unit of        formula (I) and a total number of silicon atoms per molecule at        least equal to 2,    -   an effective amount of at least one cationic initiator,    -   optionally, at least one organic solvent,    -   optionally, at least one crosslinkable and/or polymerizable        silicone monomer, oligomer and/or polymer comprising at least        one unit of formula (II),    -   optionally, at least one crosslinkable and/or polymerizable        silicone monomer, oligomer and/or polymer comprising at least        one unit of formula (III) or one perfluoropolyether compound of        formula (IV).

The present invention also features a process for preparing a hardcoating on a support based on at least one thermoplastic, comprising thestages:

-   -   a) mixing a non-functionalized colloidal silica with:        -   at least one crosslinkable and/or polymerizable silicone            monomer, oligomer and/or polymer comprising at least one            unit of formula (I) and a total number of silicon atoms per            molecule at least equal to 2,        -   an effective amount of at least one cationic initiator,        -   optionally, at least one organic solvent,        -   optionally, at least one crosslinkable and/or polymerizable            silicone monomer, oligomer and/or polymer comprising at            least one unit of formula (II),        -   optionally, at least one crosslinkable and/or polymerizable            silicone monomer, oligomer and/or polymer comprising at            least one unit of formula (III) or one perfluoropolyether            compound of formula (IV),    -   b) applying the mixture obtained to the support based on at        least one thermoplastic, and    -   c) curing the composition by crosslinking by the thermal or        actinic route to provide a hard coating.

Use may advantageously be made, so as to obtain a thin layer of hardcoating of less than 5 microns, of a volatile organic solvent which isevaporated before irradiation. The solvent is volatilized beforeirradiation but can also react with the base, in the case of thealcohols which react with the oxirane functional groups during theprocess. In this case, a reactive diluent is present.

Finally, the present invention features hard coatings obtained from thesubject compositions or by the process according to the invention.

In order to further illustrate the present invention and the advantagesthereof, the following specific examples are given, it being understoodthat same are intended only as illustrative and in nowise limitative. Insaid examples to follow, all parts and percentages are given by weight,unless otherwise indicated.

EXAMPLES

The products used in the compositions of the examples are as follows:

-   -   the silicone oligomer comprising an epoxide functionality of        formula (A) having approximately 5% of (A′)    -   the onium borate initiator (P1):    -   the colloidal silicas:

Highlink OG (OG1-32 (ethylene glycol), OG8-32 (pentanediol), OG401-31(ethylene glycol monopropyl ether), OG502-30 (isopropanol), OG502-31(isopropanol) or OG600-51 (butyl acetate)), sold by Clariant®,

Nanopox from Hanse Chemie, such as Nanopox XP 22/0314, which arereinforced with a cycloaliphatic epoxy resin.

-   -   Fumed silicas treated with acrylates, such as Aerosil R711 or        Aerosil R7200 from Degussa.

EXAMPLE 1 Preparation of a Flexform 40 Thermal Control Formulation

This solution is sold by Exxene for abrasion-resistant coatings.

This solution is applied by dipping to a polycarbonate sheet at 20° C.and is then dried at 25° C. for 10 min, followed by thermal crosslinkingat 122° C. for 35 min.

The thickness of the film is two micrometers. A Taber abrasionresistance test is carried out according to standard T30-015 with a loadof 500 g and 300 cycles with CS10-F abrasive wheels. A variation ingloss of 10% is found. % Haze=10%.

The pencil hardness of the coating ranges from 4 H to 6 H.

EXAMPLE 2 Preparation of a UV Formulation According to the InventionWithout Anti-Mist Agent

10 g of siloxane resin having a content of monomer (A) of greater than90%, obtained by hydrosilylation of 4-vinylcyclohex-1-ene epoxide(VCMX), 1.25 g of photoinitiator systems including 20% of photoinitiatorP1 dissolved in isopropanol, and 40 g of Highlink colloidal silica as a30% solution in isopropanol are charged to a beaker.

The system is stable at ambient temperature for at least 6 months withthe exclusion of light and heat. The solution is applied by dipping to apolycarbonate sheet.

The sheet is allowed to drain for one minute.

The system is crosslinked by passing, at the rate of 5 m/min, over a UVbench equipped with two 160 W/cm Hg lamps. The system is dry and veryhard at the outlet of the bench.

The thickness of the film is 3 micrometers.

The pencil hardness is 3 H immediately and greater than 4 H after 24hours.

An annealing at 150° C. for 1 hour or under an infrared lamp for a fewminutes makes it possible to obtain a hardness of 5 H.

The same Taber abrasion test is used and a variation in gloss, %Haze=15%, is found.

EXAMPLE 3 Preparation of a UV Formulation According to the Inventionwith Anti-Mist Agent

10 g of siloxane resin having a content of monomer (A) of greater than90%, 1.25 g of photoinitiator system including 20% of photoinitiator P1dissolved in isopropanol, 40 g of Highlink colloidal silica in solutionin isopropanol, and 0.5 g of silicone polyether Rhodorsil Oil 10646 arecharged to a beaker.

The system is stable at ambient temperature for at least 6 months withthe exclusion of light and heat. The solution is applied by dipping to apolycarbonate sheet.

The sheet is allowed to drain for one minute.

The system is crosslinked by passing, at the rate of 5 m/min, over a UVbench equipped with two 160 W/cm Hg lamps. The system is dry and veryhard at the outlet of the bench.

The thickness of the film is 3 micrometers.

The pencil hardness is 3 H immediately and greater than 4 H after 24hours.

The same Taber abrasion test is used. A variation in gloss of 10% isfound.

The polycarbonate glass, placed in a refrigerator at 5° C., does notfill up with mist when it is removed from the refrigerator and placed inan atmosphere at 100% relative humidity and 25° C.

EXAMPLE 4 Preparation of a UV Formulation According to the Inventionwith Anti-Fouling Agent

10 g of siloxane resin having a content of monomer (A) of greater than90%, 1.25 g of photoinitiator system including 20% of photoinitiator P1dissolved in isopropanol, 38 g of Highlink colloidal silica in solutionin isopropanol, and 2 g of polyfluorosilane,tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane, are charged to abeaker.

The system is stable at ambient temperature for at least 6 months withthe exclusion of light and heat. The solution is applied by dipping to apolycarbonate sheet.

The sheet is allowed to drain for one minute.

The system is crosslinked by passing, at the rate of 5 m/min, over a UVbench equipped with two 160 W/cm Hg lamps. The system is dry and veryhard at the outlet of the bench.

The thickness of the film is 3 micrometers.

The pencil hardness is 3 H immediately and greater than 4 H after 24hours.

However, a thermal post-crosslinking is carried out at 100° C. for 1hour in order to be certain of removing traces of unreactedalkoxysilane.

The same Taber abrasion test is used. A variation in gloss of 10% isfound.

Conventional inks do not leave a mark on the surface of the coating, incontrast to the thermal control based on colloidal silica andalkoxysilanes.

Each patent, patent application, publication and literaturearticle/report cited or indicated herein is hereby expresslyincorporated by reference.

While the invention has been described in terms of various specific andpreferred embodiments, the skilled artisan will appreciate that variousmodifications, substitutions, omissions, and changes may be made withoutdeparting from the spirit thereof. Accordingly, it is intended that thescope of the present invention be limited solely by the scope of thefollowing claims, including equivalents thereof.

1. A silicone composition cationically crosslinkable into a hardcoating, comprising colloidal particles of non-functionalized silica andwhich additionally comprises: at least one crosslinkable and/orpolymerizable silicone monomer, oligomer and/or polymer comprising: atleast one structural unit of formula (I):Z¹(R⁰)_(a)SiO_((3−a)/2)  (I) in which: a=0, 1 or 2; the radicals R⁰,which may be identical or different when a>1, are each an alkyl,cycloalkyl, aryl, vinyl, or alkoxy radical, or a hydrogen atom; theradicals Z¹, which may be identical or different when the number ofunits of formula (I) is greater than 1, are each an organic substituentcomprising at least one epoxy and/or alkenyl ether and/or oxetane and/ordioxolane and/or carbonate reactive functional group; and a total numberof silicon atoms per molecule at least equal to 2; and an effectiveamount of at least one cationic initiator; and optionally, at least oneorganic solvent.
 2. The silicone composition as defined by claim 1,further comprising, as anti-mist compound, at least one crosslinkableand/or polymerizable silicone monomer, oligomer and/or polymercomprising at least one structural unit of formula (II):Z²(R⁰)_(a)SiO_((3−a)/2)  (II) in which: a=0, 1 or 2; R⁰ is as definedabove; the radicals Z², which may be identical or different when thenumber of units of formula (II) is greater than 1, is an organicsubstituent comprising at least one oxyalkyl or polyoxyalkyl functionalgroup ((CH₂)_(m)O)_(x) or (CH₂—CH(CH₃)—O)_(y) or copolymers, saidmonomer, oligomer and/or polymer exhibiting a viscosity of less than 500mPa·s.
 3. The silicone composition as defined by claim 1, furthercomprising, as anti-fouling compound, at least one crosslinkable and/orpolymerizable silicone monomer, oligomer and/or polymer comprising atleast one structural unit of formula (III):Z³(R⁰)_(a)SiO_((3−a)/2)  (III) in which: a=0, 1 or 2; the radicals R⁰,which may identical or different, are each an alkyl, cycloalkyl, aryl,vinyl, or alkoxy radical, or a hydrogen atom; the radicals Z³, which maybe identical or different when the number of units of formula (III) isgreater than 1, are each an organic substituent comprising at least one(C_(n)F_(2n+1))—(R⁰)_(a) group with n<20, and/or one perfluoropolyethercompound of formula (IV):Y—(C_(a)F_(2a)O)_(b)—C_(a)F_(2a)—Y  (IV) in which: Y is a polymerizablegroup; a ranges from 1 to 7; b ranges from 1 to 300, such that saidperfluoropolyether compound has an average molecular mass of from 500 to20,000.
 4. The silicone composition as defined by claim 2, furthercomprising, as anti-fouling compound, at least one crosslinkable and/orpolymerizable silicone monomer, oligomer and/or polymer comprising atleast one structural unit of formula (III):Z³(R⁰)_(a)SiO_((3−a)/2)  (III) in which: a=0, 1 or 2; the radicals R⁰,which may identical or different, are each an alkyl, cycloalkyl, aryl,vinyl, or alkoxy radical, or a hydrogen atom; the radicals Z³, which maybe identical or different when the number of units of formula (III) isgreater than 1, are each an organic substituent comprising at least one(C_(n)F_(2n+1))—(R⁰)_(a) group with n<20, and/or one perfluoropolyethercompound of formula (IV):Y—(C_(a)F_(2a)O)_(b)—C_(a)F_(2a)—Y  (IV) in which: Y is a polymerizablegroup; a ranges from 1 to 7; b ranges from 1 to 300, such that saidperfluoropolyether compound has an average molecular mass of from 500 to20,000.
 5. The silicone composition as defined by claim 1, said at leastone cationic initiator comprising a cationic moiety selected from amongonium ions of formula (V):[(R¹)_(n)-A-(R²)_(m)]⁺  (V) in which: A is an element from Groups 15 to17 of the Periodic Table; R¹ is a C₆-C₂₀ carbocyclic or heterocyclicaryl radical, said heterocyclic radical optionally comprising nitrogenor sulfur as heteroelements' R² is R¹ or a linear or branched C₁-C₃₀alkyl or alkenyl radical, said R¹ and R² radicals optionally beingsubstituted by a C₁-C₂₅ alkoxy, C₁-C₂₅ alkyl, nitro, chloro, bromo,cyano, carboxyl, ester or mercapto group; n is an integer ranging from 1to v+1, v being the valency of the element A; m is an integer rangingfrom o to v−1, with n+m=v+1.
 6. The silicone composition as defined byclaim 5, the anionic moiety of the initiator comprising a borate offormula (VI):[BX_(a)R_(b)]⁻  (VI) in which: a and b are integers ranging, for a, from0 to 3 and, for b, from 1 to 4, with a+b=4; the X symbols are each: ahalogen atom, with a=0 to 3, an OH functional group with a=0 to 2; the Rsymbols, which are identical or different, are each: a phenyl radicalsubstituted by at least one electron-withdrawing group, and/or by atleast 2 halogen atoms when the cationic moiety is an onium of an elementfrom Groups 15 to 17 of the Periodic Table, a phenyl radical substitutedby at least one electron-withdrawing element or group, when the cationicmoiety is an organometallic complex of an element from Groups 4 to 10 ofthe Periodic Table, or an aryl radical comprising at least two aromaticrings, optionally substituted by at least one electron-withdrawingelement or group whatever the cationic moiety.
 7. The siliconecomposition as defined by claim 1, said at least one initiator beingselected from the group consisting of: [(C₈H₁₇)—O-Φ-I-Φ]⁺ [B(C₆F₅)₄]⁻,[(CH₃)₂—-Φ-I-Φ-CH₃]⁺ [B(C₆F₅)₄]⁻ [C₁₂H₂₅-Φ-I-Φ]⁺ [B(C₆F₅)₄]⁻,[(C₈H₁₇—O-Φ)₂I]⁺ [B(C₆F₅)₄]⁻ [(C₈H₁₇)—O-Φ-I-Φ]⁺ [B(C₆F₅)₄]⁻, [(Φ)₃S]⁺[B(C₆F₅)₄]⁻ [(Φ)₂S-Φ-O—C₈H₁₇]⁺ [B(C₆H₄CF₃)₄]⁻, [(C₁₂H₂₅-Φ)₂I]⁺[B(C₆F₅)₄]⁻ [(CH₃)₂—CH-Φ-I-Φ-CH₃ ⁺ [B(C₆H₃(CF₃)₂)₄]⁻(η⁵-cyclopentadienyl)(η⁶-toluene)Fe⁺ [B(C₆F₅)₄]⁻(η⁵-cyclopentadienyl)(η⁶-1-methylnaphthalene)Fe⁺ [B(C₆F₅)₄]⁻(η⁵-cyclopentadienyl)(η⁶-cumene)Fe⁺ [B(C₆F₅)₄]⁻
 8. The siliconecomposition as defined by claim 1, said at least one cationic initiatorcomprising a nontoxic onium salt having a cationic structure of formula(VII):[(CH(CH₃)₂-Φ-)-I—(—R¹)]⁺  (VII) in which R¹ is the -Φ-R² radical, R²being a linear or branched alkyl radical having from 1 to 20 carbonatoms.
 9. The silicone composition as defined by claim 8, the anionicstructure of the onium salt being selected from the group consisting of:Cl⁻, Br⁻, BF₄ ⁻, PF₆ ⁻, CF₃SO₃ ⁻, N(SO₂CF₃)₂ ⁻, CH(SO₂CF₃)₂ ⁻, B(C₆F₅)₄⁻, B(PhOCF₃)₄ ⁻, SbF₆ ⁻and/or AsF₆ ⁻.
 10. The silicone composition asdefined by claim 1, comprising a silicone oligomer having the followingformula (VIII):Z⁴Si(R⁰)_(a)O_((3−a)/2)  (VIII) in which: a=0, 1 or 2; the radicals R⁰,which may be identical or different, are each an alkyl, cycloakyl, aryl,vinyl, or alkoxy radical, or a hydrogen atom; Z⁴ is selected from amongthe following radicals:


11. The silicone composition as defined by claim 3, wherein Z³ is aperfluoropolyether compound selected from the group consisting of:(C₂H₅O)₂CH₃SiC₃H₆NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₃H₆SiCH₃(OC₂H₅)₂,(C₂H₅O)₃SiC₃H₆NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₃H₆Si(OC₂H₅)₃,F(CF(CF₃)CF₂O)₂₅CF₂CF₃, C₄H₉NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₄H₉,CH₂═CHCOO₂H₄NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHC₂H₄OOCCH═CH₂,(HOCH₂)₂CH₂NHCO(CF₂O)₁₅(C₂F₄O)₁₃CF₂CONHCH₂(CH₂OH)₂,(C₂H₅O)₃Si(CH₂)₃NHCO(CF₂CF₂O)₈CF₂CONH(CH₂)₃Si(OC₂H₅)₃,(C₂H₅O)₂CH₃Si(CH₂)₃NHCO(CF₂CF₂O)CF₂CONH(CH₂)₃SiCH₃(OC₂H₅)₂,(C₂H₅O)₂CH₃Si(CH₂)₃NHCO(CF₂CF₂O)₁₄CF₂CONH(CH₂)₃SiCH₃(OC₂H₅)₂,(C₂H₅O)₃Si(CH₂)₃NHCO(CF₂C(CF₃)FO)₁₂CF₂CONH(CH₂)₃Si(OC₂H₅)₃,(C₂H₅O)₂CH₃Si(CH₂)₃NHCO(CF₂C(CF₃)FO)₁₂CF₂CONH(CH₂)₃SiCH₃(OC₂H₅)₂ orOOCCH═CF₂ OOCCH₂H₂═HCCOO—CH₂CHCH₂NHCO(CF₂O)₁₅(CF₂CF₂O)₁₃CF₂CONHCH₂CHCH₂—OOCCH═CH₂ 12.The silicone composition as defined by claim 1, said silica particleshaving a mean diameter of less than 1 μm
 13. The silicone composition asdefined by claim 1, comprising an alcoholic solvent.
 14. The siliconecomposition as defined by claim 13, the proportion of organic solventbeing at least equal to 10 parts by weight.
 15. The silicone compositionas defined by claim 1, in crosslinked state.
 16. A substrate having ahard, anti-mist/anti-fouling coating of the silicone composition asdefined by claim
 15. 17. A thermoplastic substrate having a hard,anti-mist/anti-fouling coating of the silicone composition as defined byclaim 15.